Hair growth and renewal are mainly determined by the activity of hair follicles and their matrix environment.
The hair follicle is a complex autonomous cutaneous annex that comprises six large compartments, some of dermic origin (connective tissue sheath and hair papilla), others of an epithelial nature (inner and outer root sheath, hair shaft and sebaceous gland). At the base of the follicle the matrix is found, which is the site of intense mitotic activity, at the origin of 3 concentric layers of hair essentially constituted of keratin.
The hair follicle renews in situ in a cyclic and asynchronous manner from a double reservoir of stem cells, according to an activity cycle that comprises three phases: The anagen phase, the catagen phase and the telogen phase.
The anagen phase (growth phase) lasts from one to ten years and is characterized by the constant elongation of the hair. During this phase, the outer root sheath cells overexpress beta 1 integrin (Commo & Bernard, 1997, Cell mol. life Sc. 53:466-471). The proliferative cells from this area express proliferation markers such as the Ki67 protein and the p63 transcription factor (Chikh et al., 2007, Biochem Biophys Res Commun., 14; 361(1):1-6).
The following catagen phase is very transient and lasts some weeks. It seems to be initiated by certain factors such as EGF, TGF beta (Foitzik et al. 2000, FASEB J. 14(5):752-60), or else the p53 protein that is temporarily overexpressed (Botchkarev et al., 2001, Am. J. Pathol. 158(6): 1913-1919). During this phase, the follicle cells undergo an active apoptosis process, the follicle atrophies and retracts to the surface, with the well-known exception of the hair papilla that will be the key element in future regeneration.
The terminal phase or telogen phase, which lasts some months, corresponds to a follicle rest phase at the end of which the hair finishes by falling. At the end of this rest period, a new follicle is regenerated and a new cycle starts.
In addition, it has been clearly described that the differentiation mechanisms of keratinocytes from the epidermis and hair follicle are substantially different. Therefore, it is known that keratins from the hair shaft represent a family of keratins that is distinct from that expressed in the epidermis (Langbein et al., 2001, J. Biol. Chem. 276), thus the K6irs keratin (Porter et al., 2001, Br. J. Dermatol. 145: 558-568) is expressed in the inner sheath of the hair follicle but not in the epidermis, while epidermal differentiation markers such as K1 and K10 keratins are not expressed in the hair follicle (Lenoir et al., 1988, Dev. Biol. 130: 610-620).
The natural fall or loss of hair may be estimated, on average, as a hundred hairs per day for a normal physiological condition. This ongoing renewal process may be disturbed by many extrinsic and intrinsic factors, leading to a significant loss of hair, temporary or definitive, that may be grouped together under the generic term of alopecia.
As with the rest of the organism, the ongoing physiological hair renewal process is subject to aging. Whereas the most visible sign of hair aging is the graying of hair, the quality of the biological environment of the hair follicle is also affected. From among the manifestations of hair aging are observed a lesser protein synthesis of the extracellular matrix (collagen, laminin, fibronectin), leading to a loss of elasticity and tonus of the subcutaneous tissue. There is also a reduction in the consistency and organization of hair follicles, a reduction in the anagen phase duration and an extension in the telogen phase duration (Courtois et al., 1995, Br. J. dermatol., 132:86-93). In fact, the hair loses its elasticity, it is more fine and therefore more fragile. With regard to the entire scalp, aging is manifested by a lowering in capillary density and by the progressive reduction in follicle diameter, giving the hair a poorer, more sparse appearance (Pelfini, C. et al., J. Méd. Esth. Et Chir. Derm 1987; Birch M P et al. Br. J. Dermatol 2001; 144:297-304).
Independently from intrinsic aging, alterations in the hair or hair follicle may be produced during external stresses. In fact, whereas the hair has a remarkable stability, certain external factors, such as the sun, responsible for photoaging, free radicals, pollution or else certain inappropriate treatments may result in a premature deterioration in the hair structure and depletion of follicles.
The expression “external stress” is understood to refer to stresses that the environment may produce. By way of example, stresses such as pollution, UV radiation or else products with an irritating character such as surface active agents that are too detergent, colorings and bleachings, too frequent permanents or hair straightening treatments, mechanical stresses such as the rubbing of clothes, hair styles causing repeated stretching of the hair, too intense brushing, blow-dryings and drying with air that is too hot may be cited. Pollution is understood to refer to both “external” pollution, due for example to diesel particles, ozone or heavy metals and to “internal” pollution, that may be particularly due to the emissions from paint, adhesive or wallpaper solvents (such as toluene, styrene, xylene or benzaldehyde), or else to cigarette smoke. These external stresses result in an alteration in the external structure of the hair and in its mechanical properties, but may also affect the hair follicle and cause premature aging.
The cosmetic or pharmaceutical industry always seeks compositions eliminating or reducing hair loss or stimulating hair growth. As a known molecule, 2,4-diamino 6-piperidinopyrimidine 3-oxide or “minoxidil” (patents U.S. Pat. No. 4,139,619 and U.S. Pat. No. 4,596,812) may be cited. Another patent document by Shiseido (JP 07316023) also describes the use of arginine and its derivatives in the treatment of alopecia. Lastly, document EP 1885323 describes the use of a synthetic peptide to stimulate hair growth.
However, certain available products present side effects, such as in the case of minoxidil, or have a relative effectiveness confined to the treatment duration. Also, a need remains for a novel physiologically acceptable composition to encourage hair growth and/or reduce hair loss, presenting a rapid and long-lasting action.
Corn peptidic extracts have previously been described for their effects on the skin (FR 2904543, FR 2915382, FR 2925326).
The inventors have now demonstrated that such corn peptidic hydrolyzates have an activity on the hair follicle. In particular, it has been demonstrated that the peptidic hydrolyzate, when it is applied to the hair, activates the hair follicle and stimulates hair growth.